Electronic modules comprise power electronic circuits, such as inverters and rectifiers, for example. Often, a plurality of substrates is arranged on a metal base plate and integrated into a module. Metallization layers are likewise deposited on the front side (e.g. a structured layer) and the rear side of the substrates so as to connect semiconductor devices and components to the front side and the metallic base plate to the rear side of the substrate by means of soft-soldering via solder layers.
In a soft-soldering process, a solder paste is applied to the substrates by means of template printing or ink jet methods. Subsequently, the devices are placed on the solder paste surfaces. The fitted substrates are automatically transported in a soldering furnace (vacuum continuous furnace, batch furnace, vapor-phase oven, etc.). There, heat is introduced into the substrates and the solder is remelted.
Diffusion soldering provides an alternative technology to soft-soldering. During diffusion soldering, a common soft solder is used, whereby, contrary to the paste-soldering, the target layer thickness is reduced. A common heating channel may be used for diffusion soldering of semiconductor devices, which are inserted into the heating channel through an opening. The devices are soldered in an open heating channel such that a flowing forming and protective gas atmosphere and a contact pressure are present for a period of time. The heating channel is divided into three sections. For a homogeneous flow of the protective gas and for minimizing a contamination of the protective gas flow through the opening the surface of the opening is rather small so that the discharge of the protective gas only slightly disrupts the homogeneous flow of the protective gas.
The open heating channels do not provide an opportunity to use aggressive media as an activating atmosphere for the reduction of oxidized surfaces of the devices. Thus, there is a need to provide channels allowing the use of aggressive media.